1. Field of the Invention
The present invention relates to a vehicle communication system for conducting a communication between a transceiver installed in the vehicle and a mobile device to control the start of a vehicle engine and locking and unlocking of vehicle doors based on a communication result.
2. Description of Background Technology
In recent years, vehicles installed with a vehicle communication system for controlling the start of an engine and locking and unlocking of vehicle doors using a mobile device have been on the increase. Such a vehicle communication system is described with reference to FIGS. 9 and 10.
FIG. 9 is a block diagram showing a construction of a prior art vehicle communication system. The vehicle communication system shown in FIG. 9 is provided with a transceiver 10 and a mobile device 20, wherein the transceiver 10 includes a controller 21, a transmitter 22 and a receiver 23. The transceiver 10 is connected with a start detector 40 and a notifying device 50.
The start detector 40 is disposed at a specified position in the vehicle to detect that an operation button (not shown) for starting an engine has been pressed. The transmitter 22 includes an oscillating circuit and an antenna, and is disposed at a specified position in a passenger compartment. The transmitter 22 transmits a request signal requesting an authentication signal when the start detector 40 detects that the operation button has been pressed.
The mobile device 20 is card-shaped and transmits the authentication code signal upon receiving the request signal from the transmitter 22. The receiver 23 is disposed at a specified position in the vehicle to receive the authentication code signal. The notifying device 50 is disposed at a specified position in the passenger compartment to notify information representing whether or not the receiver 23 has received the authentication code signal from the mobile device 20. The controller 21 is disposed at a specified position of the vehicle and connected with the start detector 40, the notifying device 50, the transmitter 22 and the receiver 23 to control operations of the respective devices.
FIG. 10 is a diagram showing a communication area of the request signal from the transmitter shown in FIG. 9. An area A shown in FIG. 10 is the communication area of the transmitter 22 and covers a driver's seat 32 and its neighborhood in the passenger compartment of a vehicle 31, but covers neither a front passenger seat 33 nor a rear passenger seat 34.
In the above construction, when a driver presses the operation button to start the engine, this is detected by the start detector 40 and the controller 21 detects the detection by the start detector 40, whereupon the request signal requesting the authentication code signal is transmitted from the transmitter 22.
Thereafter, the controller 21 confirms a received content of the receiver 23. In the case of receiving the correct authentication code signal from the mobile device 20, the controller 21 judges that the mobile device 20 is located in the communication area A of the transmitter 22 (at and near the driver's seat), i.e. the driver is carrying the mobile device 20, a short beeping sound representing a content of the judgment is, for example, outputted from the notifying device 50, and the engine is started.
On the other hand, if no correct authentication code signal or no signal has been received from the mobile device 20, the controller 21 judges that the mobile device 20 is not located in the communication area A of the transmitter 22, i.e. the driver is not carrying the mobile device 20, causes the notifying device 50 to output several consecutive beeping sounds representing a content of the judgment, and executes such a control as not to start the engine.
A vehicle electronic key system disclosed in Japanese Unexamined Patent Publication No. H11-101033 is known as another prior art vehicle communication system. This vehicle electronic key system transmits a request signal to the inside and/or outside of a vehicle and controls devices installed in the vehicle in accordance with a response from a mobile device. If there is no response to the request signal from the mobile device, this key system increases the intensity of the request signal being transmitted and detects the presence or absence of any passenger in a passenger compartment. The key system transmits the request signal to the inside of the passenger compartment if there is any passenger in the passenger compartment while transmitting the request signal to the outside of the passenger compartment if there is no passenger in the passenger compartment.
However, in the former vehicle communication system, if the driver presses the operation button when the mobile device 20 is placed in an area outside the communication area A of the transmitter 22 (area outside the driver's seat and its neighborhood), the controller 21 causes the transmitter 22 to transmit the request signal requesting the authentication code signal, but this request signal does not reach the mobile device 20. Since the controller 21 cannot confirm the authentication code signal from the mobile device 20, the engine is not started. At this time, the driver can understand that the engine is not started because the mobile device 20 is not located at or near the driver's seat, but has no idea as to where the mobile device 20 can be. This holds for the above vehicle electronic key system, which has a similar problem accordingly.